I have a 2001 Jaguar XK8 convertible with approximately 119,000 miles on it. When I fill the gas tank up and I drive it 30 to 40 miles miles this happens. . When the gas gauge shows 3/4 and 1/2 or 1/4 I get the message check fuel cap. I turned the car off and it sits a little while and then restart it the message goes away until the gage hits the next quarter and then the message comes back. It just seems very strange that every time the gas gauge hits 3/4 and 1/2 and 1/4 marks the check fuel cap comes on and goes off after the car sits a little bit. Any ideas would be helpful. Thanks Doug

 

If removing and replacing the cap doesn’t fix anything then try replacing it. I had a similar problem when I purchased my car. A new cap fixed it . Seven plus years later still good.

Z

 

I have not had any luck with the aftermarket or auto store fuel caps. If replacing the fuel cap with a genuine Jaguar part doesn't resolve the issue, have the car scanned for diagnostic trouble codes. The Engine Control Module (ECM) has detected a small leak in the Evaporative Emissions (EVAP) system, and the most common cause is a failing gas cap seal. But there are other potential leak points. You may find a code such as P0442 stored.

Incidentally, the ECM only checks for EVAP leaks when the fuel tank is 15% to 85% full, but I don't know why this might correlate with the Check Fuel Cap warning illuminating specifically at the 1/4, 1/2 and 3/4 marks on the gauge.

Cheers,

Don

 

The fuel tank levels that you mention are the defining points between which the EVAP system is monitored for readiness. The readiness monitors (of which the EVAP is but one) will not usually throw a code or check engine light, but they have to be cleared before a smog test in CA. We had to replace an EVAP valve to get ours to pass smog a few years back. Most (actually every shop I went to) service places will tell you that you just need to drive it more to clear them. Sometimes they actually need some parts replaced. Most scan tools will report the readiness monitor status.

 

had the same problem. like mentioned above: evap valve not working.

it is above the car infront of the right wheel near to the evap canister.

you can test it if you got it on your work bench by trying to trigger the magnetic valve with a 12v battery

 

The message is telling you that you have a slight evap leak.. First make sure that the fuel cap is on tight. If the message comes back then take WD40 or other lubricant / cleaner and clean off the gas tank intake and put some lubricant on the gas cap gasket. Of course if the gasket on the gas cap looks bad then get a new cap.
If that does not work find out what ODB codes you are getting. On my car it turned out to be the cannister close valve. The OBD codes will help to steer you in the right direction.